Portable excavator



Aug. r26, 1941.

F. L. WHITE PORTABLE EXCAVATOR Filed Feb. 1o, 194o INVETOR. FRED L.WH/TE Aug. 2s, 1941. F. WHITE 2,254,192

PORTABLE EXCAVATOR I Filed Feb. l0, 1940 4 Sheets-Sheet 4 INVENToR. FREDL. -WH/TE Patented Aeg. 2e, 1941 UNirEo STATES PATENT' oFFlcE PORTABLEEXCAVATOR `Fred L. White, Marlon, Ohio. assigner. to The Osgood Company,Marlo of Ohio n, Ohio, a corporation Application February l0, l940,Serial No. 318,332

21 Claims. (Cl. 180-9-2) eliminate the inflexible linkage mechanism ofthe straight mechanical types of hand operated steering mechanisms.

A still further object of the invention is to provide a simple. easilyoperated pressure fluid valve system to control steering of theexcavator traction device and thereby eliminating the cumbersome leverlinkage for steering crawler or claims and any and all alterations,modifications and variations coming vwithin the spirit and scope of theinvention are deemed to be included herein.

In the drawings:

Figure 1 shows a top plan view of the tractio device of a portableexcavator incorporating thel invention.

Figure 2 shows side elevational view of the essential control elementsof the steering mechanism.

Figure 3 shows a vertical sectional view of the power transmission meanstothe traction device taken substantially along the line 3-3 ofl Fig-.ure 2'. i

Figure 4 is an enlarged vlew of the upper part of Figure 3 to showdetails thereof.

ing the traction holding device incorporated into the crawlertransmission.

Figure 7 is a view similar to Figure 2 but showing in addition the endelevational view of the holding device in relation to the crawlertreads.

The directional control of a crawler type of traction device customarilyemployed in connection with the portable type of excavators has in thepast always been accomplished by-a very trying and difficultmanipulation of levers to engage and disengage the clutches and brakesthat control one or the other of the two surface contacting elementswhereby a steering of the device is effected. It has customarily beennecessary to stop the traction device in orderto effect such steering.`The applicant vhas therefore developed a device which does away with thelaborious hand operated deviceand has provided a motor operated controlwhereby the steering of the traction device is performed while theexcavator is traversing the ground and may also be operable while thedipper is being employed. r

. With the above in mind, the device in its preferred embodimentcomprises initially a frame l on which are rotatably mounted treads ortraction devices 2 andl 8, mounted in suitable ways well known to theart, and which serve to drive the device in any desired direction. f Theframe i mounts sprockets 4 carried on shafts 5 and 8 additionallysupported in outboard bearings 1 and 8. The frame mounts a drive lshaft9 rotatably supported therein and whichis provided with sprockets ateach end thereof. Roller chains ill and Il are connected between thesprockets carried on shaft 9 and the sprockets carried on shafts 5and'B. Clutch elements i2 and I3 are Figure 5 is la schematic viewshowing the essentia! elements ofl the-control lin relation to therotatable platform of the excavator.

Figure 6 is a view similar to Figure l but show'- 55 mounted on theshaft I and are adapted to be selectively engaged with the sprocketscarried on shaft 9 to transmit power to the roller chains that drivetreads, 2 and 3. Shaft 8 carries a bevel gear i4 that engages a bevelgear l5 having Y -a squared hollow shank or hub carried inthe portion ofthe machine that supports the rotatable platform hereinafter descrihed.

Secured to the sprocket hubs i6 and Il are appropriate brake drums withwhich brakes I8 and Il operate. The general purpose of the .two brakesis to lockA one sprocket againstrotation while the corresponding clutchis disengaged and with the other sprocket connected to the shaft mayrotate the corresponding tread and thereby enable the moving tread totwist-the traction device to steer the excavator in any desired direcftion.

Mounted von the `frame I is a supporting strucassociated. Appropriatebearing structure '2,2' is provided that enables a relative rotationbetween portions 2| .and 22. Centrally disposed ofthe aforementionedstructure is a hollow shaft 24 having squared ends to which bevel gearI5 is 10 rigidly secured and which'has at its upper end a second gear 25that is telescope'd and journaled in sleeve 2|. The gear 25 having asquared center opening is connected to an appropriate source of powerwell known in the art. Secured t0 the housing 22 is a gear 23 rotatablymounted on shaft 23' that is appropriately connected to the source ofpower hereinbefore described whereby the cab platform 23 may be rotatedat lthe will of the operator The sq'uared openings in gears I5 and 25press iit snugly over the squared ends of shaft 24 to prevent relativerotation of the parts. Appropriate transmissions likewise well known inthe art are provided to accomplish the foregoing result. It should beapparent that the structure thus far described is more or lessconventional in character and is intended to lay the background for thatwhich isconsidered to be new and novel in the instant case.

It has been stated that the steering of the traction device of theexcavator is accomplished by stopping .the motion of one of the treads 2and 3 and permitting the other to move depending upon the direction inwhich it is desired to steer the machine. In'the instant case a singleacting pressure uid motor '21 is mounted on the frame I and is providedwith a piston rod 23 secured to a piston (not shown). The piston rod ispivotally connected to a bar member 23 which in turn is pivoted to theframe I upon pivot 33. Each bar clutches I2 and I3 and is adapted toengage or disengage the clutches with the sprocket and brake memberscooperating therewith. Bar 23 is further provided with a suitablelinkage 35 that is connected to a pivotally mounted bell crank lever 32supportedon the frame l. A brake actuator lever 34 has connected theretoa rod 33 that is connected to one arm of the swingable bracket 32. Amember 33 directly secured to frame I pro vides themeans for supportingthe swingable bracket member 32 on the frame I. Bar 23 has a second rod31 pivotally secured thereto which is engaged at one end by a'coiledcompression spring 31a. The purpose of each of the springs 31a is torelease the brake I3 and to engage the clutch I2 or I3 upon the releaseof the pressure fluid from the motors 21. The normal operatingconvdition is for the clutches to be engaged and the brakes disengaged.The rsprings 31a normally maintain this condition. Each ibrake andclutch actuator is provided .with identical linkage mechanism connectingsame with motors 21 for operating the brake and clutch mechanismsmounted uon each end of the shaft 3.

423 is equipped with a yoke 3| that engages with form to the motors 21mounted on the relatively stationary frame l. Conduite 33 are connectedbetween the inlet to the motors 21 and a head 33 that is mounted nearthe lower end of shaft 24, gear I5 and housing 23. Head 33 is mounted onthe lower end of a tube 43. The tube 43 is nxed relatively in' the shaft24 and is partly maintained in position by means of a plate 4| securedin part in support 23 fastened to or integral with the frame I. The head33 is directly supported upon the plate 4|.

Within the tube 43 are two conduits 42 and 43. 'Ihe conduitsl 42 vand 43are directly connected to each conduit 33 through the head 33 and extendupwardly and are connected ,to passageways 44 and 45 provided in core 43of rotary coupling 41.

.The rotary coupling further consists 'of a casing 43 that is removablysecured to a portion of the platform 23. As has been previouslyindicated a core 43 is relatively stationarily fixed with respect to thecasing. In order that pressure fluid may be admitted to the conduits' 42and 43 in any rotational position of the cab platform 23 sleeve 43 hasbeen provided that is secured by means of studs 53 and hexagonal nuts 5|to the core 43 as more'particularly shown in Figure 4. The casing 43 hassecured thereto conduits 51 and 53 which connect directly with conduits43 and 42 respectively through the passageways 44 and 45. 4To provide ameans for transmitting this pressure fluid from one set of conduits tothe other a pair of grooved rings 53 and 55 have been provided thatconnect directly with the passageways 44 and 45.

Each of the rings 53 and 55 is externally and internally grooved andprovided with a plurality of apertures 53 and 33 whereby the pressurefluid is transmitted to the passageways 44 and 45 located in the core ofthe rotatable couplings. Suitable packing rings 52, 54 and 53 areinterposed betweenthe rings, the sleeve 43. the casing and the core toprevent the leakage of pressure fluid to the atmosphere and from the oneconduit to the other. The core 43 is provided at its lower ,end with aflange 3| which4 is engaged on the one side by the packing ring 53 andon the 'the studs 53 that the sleeve element 43 tends to compress thepacking rings 52, 54 and 53 and that the tube 43, in connection with thehead 33 and the head 33 supporting the plate 4I, is maintained in arigid position and that the-tubular construction of the conduitsupporting elements enable the tube 43 to keep the predeter-l minedposition of adjustment. It is further evident Ythat the aforementionedtube is particularly resistant to torsionalstrains imposed thereon byreason of the rotation of the casing 43 relative to the core 43 and thesleeve 43 and associated structures.

The control of the admission of pressure uid to the motors 21 iseffected by means of a pair of conventional hand wheel or removablelever type three way valves 35 and 33 shown in Figure 3 interposedbetween a convenient source of supply and the motors 21. Valves 35 and53 are each provided with operating handles 35 and 35'; the

full lines showing, for instance, a closed position of travel. When thevalves are in the dotted position the pressure fiuid is exhausted fromthe clutch and brake motors and pressure uid coming from a source ofsupply prevented from passing the respective valves. It is obvioustherefore that the adjustment of the valves 65 and 66 will determine thedirection in which the eXcavating device is intended to turn. In Figurethere is set forth a modification of the method of control for themotors 21. The conduits 51 and 58 instead of being connected to separatevalves as in the illustration of Figure 3 are connected to a singlevalve 6l that in ect combines the two valves 65 and 66. The plunger ofvalve 61 is connected to a` lever device 6B which controls selectivelythe'application of pressure fluid to either ofthe motors 2l. A conduit69 leads to a pressure .supply 10 from the valve 51 and thepressure tankis supplied from a compressor unit H driven by an appropriate source ofpower. 'I he other levers shown in the illustration are for the controlof other parts of the excavator and do not enter into the subject of theinstant invention.

form adapted to selectively actuate said motors to selectively brakeeither of said surface con tacting elements to thereby steer saidtraction device.

2. In a power steering mechanism for a traction device, a main drivingshaft, a pair of surface contacting elements, a pair of clutches mountedon said shaft, means operatively associating said clutches with saidcontacting elements, a. pair of brakes mounted on said shaft,

said brakes and said clutches being interlocked such that when'one ofsaid brakes is applied said clutch associated therewith is disengagedand vice versa, pressure fluid operated means to actuate each ofv saidbrakes and clutches, a platform, rotatable means extending from saidplatform to said shaft, means in said rotatable means having a pair ofconduits therein and held sta- A safety device hasbeen incorporated intothe' control which enables the traction device to be held 1n position orstationary should there be a failure in the pressure' fiuid conduit orin thetransmission which would prevent the transmission of power to thetreads 2 and 3, should this failure occur while the excavator isstanding on an incline. Shaft S is provided with a ratchet wheel 2l thatcooperates with ratchet pawls 'i3 'and le. These pawls are swingablymounted in the device on shafts l? and during the normal operation ofthe transmission, the wheel 'l2 simply ratchets .the pawls out of theway but in the event the traction device should attempt to coast theratchets engage with the notches `-in the wheel and brake the 'coatingof the. machine down an incline. In the event it is desired to keep .thepawls i3 and i6 in a disengaged position a chain l5 secured to each ofthem is connected to a cam type handle le for keeping them disengaged.

The above is considered to so fully set forth the gist of the inventionthat anyone by studying the principles thereof set forth in the abovespecification and the accompanying drawings may reproduce the same. Thatwhich is considered new, novel and useful and which is sought to beprotected by Letters Patent of the United States is as follows.

1. In a steering mechanism for a traction device, a pair of surfacecontacting elements, means to drive each of said elements, verticallydisposed transmission means for supplying power to said driving means, aplatform rotatably supported relative to said vertical means. brakingmeans applied to each of said surface contacting elements, means toactuate said brakes, com.- prising a pair of uid pressure actuatedmotors carried on said device to actuate said brakes, a source ofpressure uid, conduits connecting said source to said motors, a portionof said conduits being centrally disposed ofV said vertical means.coupling means tohold said portion against torsional strains and mountedfor relative rotation of said transmission means. and valve means in aportion ot said conduits mounted on said plattionary and rigid withrespect to siaid rotatable means and adapted to prevent torsionalstrains being applied to said pairof conduits, conduits extending fromsaid pressure Quid deviceto said conduits in said rotatable means, asource of pressure fiuid on said platform, conduits extending from saidsource to said conduits insaid rotatable means, a valve means in each ofsaidv conduits adapted to selectively apply pressure means connectingsaid frame and platform for rotatably associating said 'platform withsaid frame, means for propelling said excavator, in.- cluding a shaftrotatably mounted in the frame and adapted to drive said tractiondevices. ro-

tatable means in said connecting means for driving said shaft, means forsteering said excavator, including a clutch and brakemounted on each endof said shaft, said clutch adapted to connect or disconnect the power tosaid treads, pressure iiuid operated means to actuate said clutches ofsaid platform, and said coupiing operatively connected to said conduitsto permit the transmission of pressure uid irrespective of the rotativeposition of said platform.

4. In a device adapted to connect the rotatable platform of a powerexcavator to the traction device, a frame securable to the tractiondevice, a second frame rotatably mounted with respect to said frame,supporting said platform and mounting a source of pressure fluid,pressure fluid governed means to drive said traction device meansrotatably connecting the two frames including a sleeved member andadapted to transmit power to said means to drive said traction devicereceiving a tubular gear shaft element rotatably mounted in said gearshaft, a

thin wall tube mounted in said sleeve, in a manner to resist torsionalstrain imposed by the rotation of said gear shaft, conduits supported insaid tube, a rotary coupling supported on said tube and said platform,conduits connecting said source of pressure fluid and the couplingconduits connected to said coupling mounted on said tube, said couplingadapted to conduct pressure fluid from one set of conduit to the otherand having means to prevent leakage of fluid from one conduit to theother irrespective of the relative rotationalv position of saidplatform, and conduits connecting said torsion tube conduit to saidpressure fluid actuated means thru a torsion tube mounted head. l

5. In a portable excavator, a traction device including a frame and apair of treads rotatably mounted thereon, a drive shaft rotatablymounted in said frame, a combination clutch and brake mounted on eachend of said shaft. said clutch adapted to operatively connect said shaftwith one of said treads, said brakes adapted when said correspondingclutch is disengaged to steer said traction device, pressure fluidmotors mounted on said frame to actuate said clutch and brake devices, aplatform rotatably mounted on 4said frame, means to rotatably mount saidplatform on said frame, means to transmit power through said connectionto said shaft. and including a tubular element, a pair of conduitscarried by said tubular elements and connected to said motor, meansrigidly mounting said conduits and tube in said connection to resisttorsional strain imposed by said power transmittingmeans, a source ofpressure huid, a rotary coupling means carried by said platform andtubular element. a pair of conduits connected between said coupling andsaid source oi' pressure fluid, said coupling adapted to transmitpressure fluid to said conduits carried by said tubular element, controlmeans to direct pressure iiuid to either of said motors, and holdingmeans means to rotatably mount said platform on said frame, a pair ofpressure fluid motors mounted on said frame for operating each of saidbrake and clutch elements, a torsion resisting tube concentricallymounted in said means to rotatably mount saidv platform, a rotatablecoupling the casing of which is fixed relative to said platform and alsosupported by said tube, a pair of conduits extending from said couplingto said motors, a second pair of conduits connecting said casing, said.pump and said valves, means in said coupling to connect said two pairof conduits irrespective of the rotational position of said platform andvalve means connected to said second pair of conduits whereby pressurefluid may be selectively applied to either .of said motors, saidcoupling permitting the transmission of pressure uid irrespective of therotational position of the platform and prohibiting leakage of pressurefluid.

8. In a portable excavator, a drive shaft mounted in a frame, arotatable platform, means to rotatably mount said platform on said frameand including a tube held against rotation therein, rotatable meansy insaid means). connected to said shaft, a pair of clutch and brakelelements mountedon said shaft, a pair of motors to actuate said clutchand brake elements, a rotary coupling mounted `on saidqtube. conduitsconnecting said motors and said coupling, a part of said conduitsrigidly held in said tube, a second pair of conduitsconnected to saidcoupling and to a source of pressure fluid, said lcoupling connectingsaid two sets of conduits irrespective of the relative rotationalposition of said coupling, and a valve means to selectively applypressure fluid to said motors.

carried by said shaft adapted to hold said traction device when eitheror both of said clutches 1is rendered inoperative.

clutches adapted to operatively connect said shaft to said treads, meansmounted on said vframe and adapted to selectively actuate said clutchand brake elements, a platform rotatably mounted on' said frame, meansextending between said frame and said platform, rotatably supporting.said platform,- power transmitting means carried by said connection andconnected to said shaft. a tubular element mounted in saidconnection,means mounting said tubular element and adapted to resist torsionalstrain in said element, a pair of conduits carriedby said tubularelement, one of said conduits being con nected to each of said motors, asource of pressure fluid for said motors, a rotatable coupling supportedon said tubular element and adapted means connected to said conduits andadapted to selectively actuate said brakes and clutches to steer saidexcavator, and means to positively hold said excavator in any oneposition upon failure of said motors or said power transmittingconnection.

'1. In a portable excavator, a frame mounting a shaft provided with apair of clutch and brake elements and adapted to drive endless tractionelements, a platform rotatably mounted on said 9. Means for actuatingthe clutch and brake mechanism of a traction device, the combination, apair of clutch and brake actuators, motor means to actuate same, acontrol means for selectively operating said motors to steer saidtraction device, said control means lcomprising a valve to selectivelydirect pressure fluid to said motors, conduits connecting said valvesvand motors, a rotatable platform on which said; valves are mounted, arotary coupling on said platform and in said conduits lines adapted totransmit pressure fluid to said motors in any rotative position of saidplatform and said coupling vincluding means to permit the n of pressureuid and without leakage to the atmosphere.

10. Ins portable excavator; a frame; traction elements mo ted on saidframe; means to drive said elemen a platform rotatably mounted on saidframe;K means to rotatably mount said platform on said frame, said meansincluding a power transmitting shaft connected to said means to drivesaid elements; lmeans to steer said frame and traction elements,including pressure fluid operated means mounted on said frame to controlto transmit pressure fluid to each of said motors,

said means to drive'said elements; valve means to control said steeringmeans mounted on said platform and rotatable therewith; conduitsconnecting saidl control and said pressure fluid operable means some ofsaid conduits extending through said shaft; tube means in said shaft tohold saidsh'aft conduits against torsional strains and coupling meansconnecting the different sections of conduits and supported on saidtube. said coupling transmitting pressure iluid such that the steeringof the excavator is possible in any rotational positionof said platform.

frame supporting a pump and control valves, 11. Inacontrol devicefcraportable excavator;

tional position of the coupling and the platform' and means to flxedlyhold said connecting means insaid shaft against torsional strains.. 12.In a steering mechanism for a traction de vice; a pair of surfacecontacting elements; means to drive each of said elements; a verticallydisposed transmission means to supply power to said driving means; aplatform rotatably supported relative to said vertical means; brakingmeans applied to said surface contacting elements; means to actuate saidbrakes; comprising pressure fluid actuated motors'; a source of pressureuid mounted on said platform; conduits connecting said source tosaidmotors; a portion of said conduitsl disposed in said'vertlcal meansand held against torsional strains; a rotary coupling connecting saidconduits in said vertical means and the conduit leading from said sourceof pressure 4iluid adapted to transmit pressure fluid in any rotationalposltionof the platform and valve means mounted on said platform toselectively actuate said moiors to braise either of said surfacecontacting elements to steer said traction device.

13. ina mechanism' adapted to rotatably support a platform on anexcavator frame; a fixed element secured to the frame; a frameassociated with .said platform; s hollow shaft connecting said elementand platform frame; means to transmit power rotatably mounted in saidshaft; and a torsion resisting tube adapted 'to support conduits mountedsoncentrieally of said shaft and extending between said element and saidplatform frame conduits mounted in said tube; a vsource of pressurefluid and control means mounted on said platform and eonnected to saidtube mounted conduits and a rotary couoiing connected between the tubeconduits and the source of pressure and control means, said couplingadapted to transmit pressure fluid in any rotational position of theplatform.

14. In a steering control for a portable excavator; a frame having powerdriven traction elements thereon; a cab platform; a hollow sleeve shaftconnecting said platform and frame for relative rotation; means to drivesaid elements including a power shaft. concentric with said hollowsleeve shaft; pressure fluid operated means to selectively apply powerto said elements to steer the excavator; means to energize and controlsaid pressure fluid means mounted'on said platform;` conduits to connectsaid platform mounted means and said pressure iluid operated means, andextending through said shafts; and

means to conduct pressure fluid in any rotational position of saidplatform, including a tube xedly held concentrically of said shafts, arotary coupling on said platformand secured :to said tube and adapted totransmit pressure fluid in any rotational position of the platform andconduits in said tube conectad to said coupling to conduct pressurefluid through said shaft and thence by said conduits to said pressure udoperated means.

15. In a portable power shovel; a drive shaft mounted in a frame; arotatable platform; means to rotatably mount said platform on said frameand including a torsion resisting tube held against .rotation therein;rotatable means in said means operably connected to said shaft; clutchand brake elements mounted on said shaft; pressure fluid means toselectively actuate said clutch and brake elements; a rotary couplingmounted on said tube and platform; conduits connecting said pressurefluid meansl and said coupling; a part of'said conduits held againsttwisting in said torsion resisting tube; conduits connectingsaldcoupling to a source of pressure fluid; said coupling connecting vsaidconduits and adapted to transmit pressure iluid irrespective of the rotational position of said couplingand said platform' and a valve meansin said conduits to selectively apply pressure fluid to said means toactuate said clutch and brake elements.

16. In a portable excavator; a frame having traction elements; aplatform; means to rotatably mount said platform on said frame; drivemeans for said traction elements; pressure fluid operable means to steersaid frame and acting on said drive means; valve means to control saidmeans to steer said frame, and mounted on said platform; and conduitsconnecting said pressure fluid operable means and said valve some ofwhich aremounted in a portion of said drive means; a tube in said drivemeans adapted to hold said conduits against torsional strains imposed byAsaid drive means; a rotary coupling which is adapted to positivelyconduct pressure fluid to said pressure fluid from said valve to saidpressure fluid operable means in any rotational position of saidplatform, said coupling being disposed above and on said tube disposedin said drive means.

17. In a power shovel; a frame having traction elements thereon; a cabplatform; means connecting said frame and platform for relativerotation; means to drive said traction elements in- Vapplication ofpressure fluidv to said steering means and mounted on said platform;conduits connecting said steering means, and said means to energize andsaid steering means, including rigid conduits mounted in said connectingmeans and fixed in a torsion tube which holds said conduits rigid; andmeans in said conduits to conduct pressure fluid in any rotationalposition of said platform which comprises a rotary drive said elements;concentric shafts connect-.-

ing said frame and said platform, one shaft rotatably supporting saidplatform and the other shaft transmitting power to said elements;pressure fluid operated means to steer said traction elements andoperably associated with said means toA drive said traction elements;valve means to control said pressure fluid means mounted on saidplatform and operable in any rotatable position of said platform;conduits connecting said means to steer. and said valve means, some ofwhich is mounted in one of said shafts, means to mount conduits in oneof said shafts including a torsion resisting tube supporting saidconduits and rotary coupling means supported on said platform and tubeto transmit through said connection to said shaft. and including atubular element. a pair oi conduits carried by said tubular elements andconnected to said motor, means rigidly mounting said conduits and tubein said connection to resist tor- ,sional strain imposed by said powertransmitpressure fluid to said pressure iluid operated r means in anyrotational position oi said platform.

19. In motor operated excavator; a frame; a pair of traction elements onsaid frame: a cab platform; shaft means connecting said frame andplatform; means to drive said elements;

l means to selectively drive either ot said traction elements to steersaid excavator including a drive shaft in said shait means; pressureiiuid operated motors to eiiect the steering oi the excavator; a sourceof pressure uid and control valves for said motors mounted on saidpiatform; means in said shaft to support a pair oi conduits comprising atorsion resisting tube means; a rotary coupling connected to said tubeand also supported on said platform: conduits connecting said coupling,said valve and `source of pressure and other conduits connecting saidtube mounted conduits and said motors; said coupling and torsion tubepermitting the transmission of pressure fluid in any rotational positionof said platform.

20. In a portable excavator. a traction device' including a frame and apair of treads rotatably mounted thereon. a drive shaft rotatablymounted in said frame, a combination clutch and brake mounted on eachend of said shaft, said clutch adapted to operatively connect said shaftwith one of said treads. said brakes adapted when said correspondingclutch is disengaged to steer said traction device. pressure iijuidmotors mounted'on said frame to actuate said clutch and brake devices. aplatform rotatably mounted on said frame. means to rotatably mount saidplatform on said frame. means to transmit power ting means. a source ofpressure iiuid. a rotary coupling means carried by said platform andtubular element. a pair of conduits connected between said coupling andsaid source of pressure iiuid. said coupling adapted to transmitpressure iiuid to said conduits carried by said tubular element, andcontrol means to direct pressure iiuid to either of said motors.

2l. In a steering device for a portable excavator. the combination. aframe. a pair oi.' treads rotatably mounted on said frame, a drive shaftrotatably mounted in the frame, a pair oi clutch and brake elementsmounted on the shaft. a pair of single acting pressure fluid motors forsaid clutches adapted to operatively connect said shaft to said treads,means mounted on said frame and adapted to selectively actuate saidclutch and brake elements. a platform rotatably mounted on said frame,means extending between said frame and said platform, rotatablysupporting said platform, power transmitting means carried by saidconnection and connected to said shaft. a tubular element mounted insaid connection. means mounting said tubular element and adapted toresist torsional strain in said element. a pair of conduits carried bysaid tubular element, one of said conduits being connected to each oi'said motors. a source o! pressure iiuid for said motors, a rotatablecoupling supported on said tubular element and adapted to transmitpressure iluid to each of said motors.

and means connected to said conduits and adapted to selectively actuatesaid brakes and clutches to steersaid excavator.

' FRED L. WHITE.

